From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 27E2121146F; Wed, 16 Apr 2025 19:34:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744832061; cv=none; b=g/EU9kR9cxKz8UEWbZP8AcluyV37kk73JbLtlhw4Bpqtug9xCkSExDlqDU5Ga/T8BRYNrb4LyrPgYhQ5bLrrA2mw5Mrl8uLil16alG8ejJqRBkxW45s/dlbE8oKOQLWSwMT97BO77cu+MjG6yCJQjRCVsQPI3LmE0zJder1tuSY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744832061; c=relaxed/simple; bh=geLExcJtOAjXjEY3nYZsjfpMc2TX5ES0OBy8m9gKC/k=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Yy005nBXdkAaHF1EwwQ8c0y9rp28Uo/T6FLQCmdaPAixt0MRl71W9muINEfO3tWan1DW7GfofxbeyYqcEsSTfbWbt0YFNf9c3yJCLJ5VZT1AiUPYf61FB/TDFjmvxDXOSIsXPCMIE1x1BYLlxFxn1W61cJz6FYTFwRbxKOi/doY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T+A0oHTS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="T+A0oHTS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1E34AC4CEE2; Wed, 16 Apr 2025 19:34:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1744832059; bh=geLExcJtOAjXjEY3nYZsjfpMc2TX5ES0OBy8m9gKC/k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=T+A0oHTSymTtL9IlRxP2X49sZVIM+qKZykeUc2U1jckOh7Fab2nVwAlbNWbp/XYXH 72yCmdRJgMazizkaUaoxG0Wn7KFWs6aHcG6OfFWYy+IW8oFbj4GScY3vpMq0460m83 znneUQQNp70DChBAFipuLJMTCbl0QPbJuB9t45gg34S2XEtV2Xy7YIWXsmuR4MnGoB ONm30k/EW8IhlQTZhxZ/RMNIYfZyo3oG6WmJH2ox1m2hZrI+VEcIhKMAYk9WTZNjB/ RizhkamT1QOnRjMZK46AjXuFi1Hwlokh2lbPLIBWcjDTJ5LJe25/TXY4xyWLb6lIOf LWfCobji2UGcQ== Date: Wed, 16 Apr 2025 22:34:16 +0300 From: Jarkko Sakkinen To: chenlinxuan@uniontech.com Cc: Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , Andrew Morton , Yishai Hadas , Jason Gunthorpe , Shameer Kolothum , Kevin Tian , Alex Williamson , Peter Huewe , Masahiro Yamada , Nathan Chancellor , Nicolas Schier , Nick Desaulniers , Bill Wendling , Justin Stitt , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, virtualization@lists.linux.dev, linux-integrity@vger.kernel.org, linux-kbuild@vger.kernel.org, llvm@lists.linux.dev, Winston Wen , Changbin Du Subject: Re: [PATCH RFC v2 4/5] tpm: add __always_inline for tpm_is_hwrng_enabled Message-ID: References: <20250416-noautoinline-v2-0-e69a2717530f@uniontech.com> <20250416-noautoinline-v2-4-e69a2717530f@uniontech.com> Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250416-noautoinline-v2-4-e69a2717530f@uniontech.com> On Wed, Apr 16, 2025 at 05:44:50PM +0800, Chen Linxuan via B4 Relay wrote: > From: Winston Wen > > Presume that kernel is compiled for x86_64 with gcc version 13.3.0: > > make defconfig > ./scripts/kconfig/merge_config.sh .config <( > echo CONFIG_TCG_TPM=y > echo CONFIG_HW_RANDOM=m > ) > make KCFLAGS="-fno-inline-small-functions -fno-inline-functions-called-once" > > This results a link error: > > ld: vmlinux.o: in function `tpm_add_hwrng': > tpm-chip.c:(.text+0x6c5924): undefined reference to `hwrng_register' > ld: vmlinux.o: in function `tpm_chip_unregister': > (.text+0x6c5bc9): undefined reference to `hwrng_unregister' > ld: vmlinux.o: in function `tpm_chip_register': > (.text+0x6c5c9b): undefined reference to `hwrng_unregister' > > With `CONFIG_TCG_TPM=y` and `CONFIG_HW_RANDOM=m`, > the functions `tpm_add_hwrng`, `tpm_chip_unregister`, and > `tpm_chip_register` are compiled into `vmlinux.o` > and reference the symbols `hwrng_register` and `hwrng_unregister`. > These symbols, however, are compiled into `rng-core.ko`, which results > in the linking error. > > I am not sure but I think this weird linking error only arises when > auto inlining is disabled because of some dead code elimination. > > `CONFIG_TCG_TPM=y` and `CONFIG_HW_RANDOM=m` set `CONFIG_HW_RANDOM_TPM=n`. > This causes the function `tpm_is_hwrng_enabled` to always return > `false`, as shown below: > > static bool tpm_is_hwrng_enabled(struct tpm_chip *chip) > { > if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM)) > return false; > if (tpm_is_firmware_upgrade(chip)) > return false; > if (chip->flags & TPM_CHIP_FLAG_HWRNG_DISABLED) > return false; > return true; > } > > When `tpm_is_hwrng_enabled` is inlined, dead code elimination > optimizations are applied and the reference to the `hwrng_*` functions > will been removed. > For instance, in the `tpm_chip_unregister` function: > > void tpm_chip_unregister(struct tpm_chip *chip) > { > #ifdef CONFIG_TCG_TPM2_HMAC > int rc; > > rc = tpm_try_get_ops(chip); > if (!rc) { > tpm2_end_auth_session(chip); > tpm_put_ops(chip); > } > #endif > > tpm_del_legacy_sysfs(chip); > if (tpm_is_hwrng_enabled(chip)) > hwrng_unregister(&chip->hwrng); > tpm_bios_log_teardown(chip); > if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) > tpm_devs_remove(chip); > tpm_del_char_device(chip); > } > > When `tpm_is_hwrng_enabled` is inlined and always returns `false`, > the call to `hwrng_unregister` is effectively part of a `if (false)` > block, which I guess that will be then optimized out. > > However, when the `-fno-inline-small-functions` and > `-fno-inline-functions-called-once` flags are used, > tpm_is_hwrng_enabled is not inline. > > And this optimization some how cannot occur, > leading to the undefined reference errors during linking. > > Adding the `__always_inline` attribute ensures that > `tpm_is_hwrng_enabled` is inlined regardless of the compiler flags. > This allows the dead code elimination to proceed as expected, > resolving the linking issue. > > Co-developed-by: Chen Linxuan > Signed-off-by: Chen Linxuan > Signed-off-by: Winston Wen > --- > drivers/char/tpm/tpm-chip.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c > index e25daf2396d37bcaeae8a96267764df0861ad1be..48cc74d84247e258a39f2118e03aa10d0cbb066a 100644 > --- a/drivers/char/tpm/tpm-chip.c > +++ b/drivers/char/tpm/tpm-chip.c > @@ -534,7 +534,7 @@ static int tpm_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait) > return tpm_get_random(chip, data, max); > } > > -static bool tpm_is_hwrng_enabled(struct tpm_chip *chip) > +static __always_inline bool tpm_is_hwrng_enabled(struct tpm_chip *chip) > { > if (!IS_ENABLED(CONFIG_HW_RANDOM_TPM)) > return false; > > -- > 2.48.1 > > > Thank you. Reviewed-by: Jarkko Sakkinen BR, Jarkko